[Andrea Beraldo]

Hi all I took the darlington uln2803a to control the pump relay on my v4.4b board but I can't get the 5v signal to drive the transistor.
When the pump turns on the PIN16 of the proto area is shorted to ground, but if I have to put a transistor, what sense does this have?
Does this mean that the PIN16 on this card is high current?
From output 45 of arduino come out 5 volts and I would not like to wildly solder a wire on this pin.
Thanks for the reply in advance !!!

[LPG2CV]

This may help, but check it's in context.

viewtopic.php?f=18&t=2390&p=29564&hilit=ULN2803#p29564

You could do an advance search on the chip and psig as the author. I'm sure he has explained it a number of times.

[Chris Wolfson]

The fuel pump pin supplies a relay with ground, you have to supply 12V+ to the other side of the relay coil. if I got it all correct. You should not need an additional transistor in the proto area.
Take care to ground connections from battery to engine, chassis and ECU. If you got any (unknown) problem there, nothing else will work as expected. The first thing I do on any install is to improve grounding, even as anything seemed to work. Often ground problems go for years unnoticed.

[theonewithin]

That board has extra low current outputs already fitted.

No extras needed.

[PSIG]

Hi all I took the darlington uln2803a to control the pump relay on my v4.4b board but I can't get the 5v signal to drive the transistor.
When the pump turns on the PIN16 of the proto area is shorted to ground, but if I have to put a transistor, what sense does this have?
Does this mean that the PIN16 on this card is high current?
From output 45 of arduino come out 5 volts and I would not like to wildly solder a wire on this pin.
Thanks for the reply in advance !!!

Correct. Using the link for ULN2803 info posted by @LPG2CV, you can see that when Mega pin 45 (at the proto area) goes HIGH, the output from the ULN on connector IDC16 goes low (grounds), with about 0.5-amp capacity. This is more than enough capacity to ground a relay for operation.

As others have stated, the relay would be supplied with VBAT to one control terminal, and connected to IDC16 on the other, in order to energize and operate the relay coil to switch the relay load. An example of your setup could be as below. The question that @theonewithin stated is why you want to use a ULN in the proto area when the v0.4.4b board already has a transistor for this purpose?

FP_relay_wiring_option_ULN.png (32.4 KiB) Viewed 3943 times

[Andrea Beraldo]

Ok I had the doubt because on the wiki I did not find information regarding my specific card.
And what about the tachometer does a PWM signal come out?
Can I attach the PIN17 directly to the instrument cluster of my E36?

[theonewithin]

Check the schematic for your board.

The tacho output is a square wave.

[Andrea Beraldo]

Ok thanks.